Triggering
The active state of an interrupt line on the S5 bus triggers the
interrupt. The interrupt signal is level-triggered (low level). To
acknowledge the interrupt, please refer to the operating instructions
for the module which triggers the interrupt.
User interfaces
OB 2 to OB 5
If an interrupt occurs, one of the OBs listed in the following table is
called as the user interface.
Interrupt triggered by OB called
Interrupt signal X
(A, B, C or D, slot-dependent)
Interrupt signal E
Interrupt signal F
Interrupt signal G
OB 2
OB 3
OB 4
OB 5
If, for example, the interrupt signal ’F’ occurs, the system program
calls OB 4.
If the relevant OB is not loaded, program execution is not interrupted.
There is no interrupt-driven program execution.
Priority of process interrupts
The default setting means that PROCESS INTERRUPTS have a lower
priority than the TIMED INTERRUPTS level.
A parameter in data block DX 0 allows you to change the default so
that the process interrupts level has a higher priority than the TIMED
INTERRUPTS level.
Within interrupt servicing, the priorities of the individual interrupts
are specified as follows:
•• If there are several interrupts pending, the corresponding
organization blocks are called according to the order of priority
you specify in DX 0 (single priority).
You can specify priority levels 1 to 5 for the four interrupts.
Table 4-8 User interfaces for interrupts
RUN Mode
CPU 948 Programming Guide
4 - 44 C79000-G8576-C848-04
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